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That seem to be all 35 wires of the visible battery harness in that picture. So where are the temperature sensors? The lower harness (narrower connector on lower left) likely runs to a temp sensor under each cell. |
MM43, #215
I suspect the reason for the present arrangement is to keep the battery management system intrinsic with the cells that it controls. Additional and unquantifiable ohmic losses could present a significant problem for remote monitoring. the electronics and (?) data logging are in the enclosure is that system is designed with enough storage capacity to log the whole life of the battery. If it's in the charger, there has to be a process to ensure continuity and accuracy of existing data. If either the battery or charger are replaced in service, the logged data will no longer match that for the battery. It's issues like that that can make system design so complex, trying to resolve all the conflicting requirements. Still doesn't excuse the unprotected boards though and they should have at least used a separate sealed compartment, as RR_NDB suggested a couple of posts prior to yours... Regards, Chris |
I think first off it is cheaper to build as a compact unit, secondly, it is easier (cheaper) to R/R as a unit and third, it conforms cleanly with the spirit of the FAA rule to isolate the pack (all of it) away from other EE equipment, in case of fire, expansive failure (explosion), electrolyte spatter, and draining thereof.
Y'all have done a great job of describing how better to build it. Know this, Boeing knows this as well. But they built it the way they built it. The reason? Also an interesting discussion. For one thing, LRU.... |
NTSB January 27 press release
Not that there is much meat there, but in case of interest there is a Sunday press release which is being reported in some press as exonerating the charger. It reads to me more like they ran through tests of electronics removed from the incident JAL aircraft at the manufacturers' sites without finding a detectable fault.
This does go some way to saying the units were not faulty compared to intention. It does nothing to allay concern that the design as intended might place eventually intolerable conditions upon the battery--at least that is my view. |
Specs
archae86:
Just abuse. That is my feeling too. The analysis of the remaining (94) batteries could clarify very well. Rgds, |
NTSB Update on JAL Boeing 787 Battery Fire Investigation
January 27 WASHINGTON - The National Transportation Safety Board today released a fourth update on its investigation into the Jan. 7 fire aboard a Japan Airlines Boeing 787 at Logan International Airport in Boston. The fire occurred after the airplane had landed and no passengers or crew were onboard. The event airplane, JA829J was delivered to JAL on December 20, 2012. At the time of the battery fire, the aircraft had logged 169 flight hours with 22 cycles. The auxiliary power unit battery was manufactured by GS Yuasa in September 2012. NTSB investigators have continued disassembling the internal components of the APU battery in its Materials Laboratory in Washington, and disassembly of the last of eight cells has begun. Examinations of the cell elements with a scanning-electron microscope and energy-dispersive spectroscopy are ongoing. A cursory comparative exam has been conducted on the undamaged main battery. No obvious anomalies were found. More detailed examination will be conducted as the main battery undergoes a thorough tear down and test sequence series of non-destructive examinations. In addition to the activities at the NTSB lab, members of the investigative team continue working in Seattle and Japan and have completed work in Arizona. Their activities are detailed below. ARIZONA The airworthiness group completed testing of the APU start power unit at Securaplane in Tucson and the APU controller at UTC Aerospace Systems in Phoenix. Both units operated normally with no significant findings. SEATTLE Two additional NTSB investigators were sent to Seattle to take part in FAA's comprehensive review. One of the investigators will focus on testing efforts associated with Boeing's root cause corrective action efforts, which FAA is helping to lead. The other will take part in the FAA's ongoing review of the battery and battery system special conditions compliance documentation. JAPAN The NTSB-led team completed component examination of the JAL APU battery monitoring unit at Kanto Aircraft Instrument Company, Ltd., in Fujisawa, Kanagawa, Japan. The team cleaned and examined both battery monitoring unit circuit boards, which were housed in the APU battery case. The circuit boards were damaged, which limited the information that could be obtained from tests, however the team found no significant discoveries. Additional information on the NTSB's investigation of the Japan Airlines B-787 battery fire in Boston can be found at Accident Investigations - Boeing 787. The NTSB will provide another factual update on Tuesday, Jan. 29, or earlier if developments warrant. To be alerted to any updates or developments, follow the NTSB on Tw!tter at www.twitter.com/ntsb. |
Hopefully the ANA circuit boards are in better condition and yield clues as to why the protections failed.
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Questions
Lyman:
From a geometric standpoint, why not cylindrical? Unfortunately we can raise a lot of questions. Itīs a sad surprise the problems for the program. :{ |
A cursory comparative exam has been conducted on the undamaged main battery. No obvious anomalies were found. More detailed examination will be conducted as the main battery undergoes a thorough tear down and test sequence series of non-destructive examinations. |
@EEngr
I'd want to see a statistically significant sample from the entire fleet I sign off until more info is made public. |
If the cells are cylindrical, bulging is better tolerated, without impacting an adjacent cell. The spaces between cylindrical cells allow for containment of electrolyte if some spills. Also cooling air, if so equipped. Even liquid coolant could be used, under low pressure. "Density" has limits....
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Remind
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I'm placing my bet on "software bug".
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Whoever has to pay the bill...., no peanuts:\
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If Miss skinnybones had two other batteries, on line, the Back Up batteries could be saved for what they were intended for, abnormals.
Making up a complex system of charging and monitoring two emergency batteres to save the weight of two standard issue batteries has cost, so far, how much? |
Lyman. The batteries may also be required for (fairly) normal ops. You're forgetting a reasonably common scenario. Powering up a dead aircraft! While it may not happen that often there are certainly cases where the aircraft will be powered up using batteries alone. Allowing for a start sequence of perhaps 90 seconds and certainly massive current draw on the APU battery, it will be seriously depleted after an APU start. This is why it needs to be charged rapidly.
Your comments on this display a lack of knowledge of airline operations & battery construction techniques among other things. As a general winge I'm also amazed at the rampant speculation and even conspiracy theories displayed in this thread. Let the NTSB do their job then perhaps we can speculate as to how Boeing will remedy the problem. :ugh: |
As a general winge I'm also amazed at the rampant speculation and even conspiracy theories displayed in this thread. Let the NTSB do their job then perhaps we can speculate as to how Boeing will remedy the problem. majority here are genuinely curious as to what went wrong. Also, possible design flaws have already been exposed. Just as open source software is often of better quality than the so called pro stuff, forums like these often have much more of a clue as to what's what because of the wide range of skills and experience of the contributors. The spirit of enquiry, enquiring minds want to know etc :-). If you think this is bad, you should try the newsgroups, where flame wars are an everyday event... Regards, Chris |
I posted this in rumours and news by mistake, but really a followon from the
previous post #222: Just a few more thoughts: If a $100 Terrabyte pc drive can have smartmon predictive failure and usage logging, one would certainly expect it to be built into a critical component such as the battery subsystem. Such diagnostics are built into a wide variety of kit as standard practice these days. On power up self test, the battery and logic can be tested before allowing it to be brought online to charge or load. Such built in test and monitoring should also be able to predict cell failure due to changes in characteristics. The fact that there's been no news about this suggests that either a) It's not built into the design, or b) The function was on the internal boards that were cooked in the fire. In either case, not very helpfull. Otherwise, it would logically be the first place to look for the events that led up to the failure. Mysterious indeed... Regards, Chris |
"Bug"
ross_M:
I'm placing my bet on "software bug". Certainly there are algorithms "conditioning" the cells. :8 :} The dangerous cells were pushed too far? During recharge? |
Read through all the various threads here with interest, and I am equally curious about the charging system.
I am an engineer although these days tend to manage others who build various systems. At one time in my career I was an EMC engineer and set up tests to try and break military comms systems using Conducted Susceptibility and Radiated Susceptibility test techniques. Doing this sort of work makes one think about systems and how they are influenced by various electrical signals, intended or otherwise. Any test of equipment or a system is only as good as the test parameters and the boundaries set. I wonder, and this is maybe speculation, if there is a possibility of cumulative degradation of a component under some form of electrical stimulus. One example of something like that occurred in the shipping industry in 2010. Link to report enclosed. Marine Accident Investigation: QM2 |
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